Frequency modulated continuous-wave (FMCW) radar systems, such as those used in automotive applications, require a low noise chirp signal with a highly linear variation in frequency with respect to time because the frequency of the detected return signal is used to infer distance. For accurate distance resolution, a high degree of accuracy in the frequency output from the chirp generator is required. In addition, a fast settling time between each chirp phase is required.
It desirable for such FMCW radar systems to be implemented within CMOS deep-submicron process semiconductor devices. However, SiGeCmos process semiconductor devices have a 5V supply advantage compared to the 1V supply used in CMOS deep-submicron process devices. Accordingly, for the same chirp dynamic range, the oscillator gain in a CMOS deep-submicron process device is required to be five times larger, with the DAC noise contribution also being increased.